Comprehensive investigation of single, double, and vacancy-ordered perovskite absorbers in planar n-i-p solar cells

Abstract Comprehensive computational investigations are conducted on single, double, and vacancy-ordered lead and lead-free perovskite solar cells using SCAPS-1D. The study focuses on optimizing the thicknesses of the absorber and charge transport layers, as well as the effects of temperature and light intensity. Six perovskite materials are considered as the absorbers of the solar cells: Cs 2 SnI 6 , Cs 2 AgInBr 6 , Cs 2 AgBiBr 6 , CsSnBr 3 , CsPbI 3 , and FAPbI 3 . TiO 2 serves as the electron transport layer (ETL), while Spiro-OMeTAD acts as the hole transport layer (HTL). Initially, six devices are simulated to analyze current density and quantum efficiency (QE) characteristics. Subsequent optimization results in a significant improvement in power conversion efficiency (PCE) compared with the initial ones. The optimized devices achieve PCE values of 19.25% for Cs 2 SnI 6 , 17.95% for Cs 2 AgInBr 6 , 10.75% for Cs 2 AgBiBr 6 , 16.69% for CsSnBr 3 , 17.72% for CsPbI 3 , and 16.14% for FAPbI 3 , where Cs 2 SnI 6 exhibits the highest efficiency due to its favorable band alignment with the ETL, higher defect tolerance, and reduced interfacial recombination losses. Correlation matrix analysis further reveals strong relationships between the above key performance parameters and absorber, ETL, and HTL layer thicknesses, indicating that interface-controlled charge transport and recombination play a dominant role in device performance optimization. Furthermore, analysis of light intensity reveals that device efficiency improves under lower illumination conditions as a result of suppressed trap-assisted recombination and reduced space-charge effects at lower carrier injection levels. Capacitance and Mott–Schottky analyses emphasize the importance of interface engineering and defect passivation in improving the electronic performance of lead-free perovskite solar cells, while Nyquist analysis confirms reduced charge-transfer resistance and efficient carrier transport across the optimized devices. These optimized results demonstrate the potential of these materials as realistic upper-bound performance benchmarks and reliable design targets for next-generation solar cells.